(In case your a youngster, two bits equals a quarter.) "Put my two cents in" originates from the older "put my two bits in" and has its origin in the game of poker. When playing poker you have to make a small bet before the cards are dealt called an "ante" to begin play in that hand. This phrase draws an analogy to the poker ante (two bits) and gains your entry into the conversation. http://members.aol.com/%20MorelandC/HaveOriginsData.htm

In any case, the whole point of "my two cents worth," which originated in the late 19th century, is that it is a faux-modest, self-deprecating tactic used to disarm your audience before you announce your opinion. This is especially important in the event that your opinion turns out to be idiotic, in which case you can always claim that you warned your listeners in advance that your opinion was next to worthless. The phrase has long since become a cliche, and its use can be especially grating when the person announcing the arrival of his "two cents worth" is a doctor or lawyer (or a dentist, come to think of it) charging you two hundred dollars an hour. Don't get me started. "Two cents" or "two-center" has been a slang synonym for "very cheap" since the middle of the 19th century, when the cheapest cigar available was literally a "two- center." The U.S. Treasury Department actually issued a two-cent coin in 1864, which was, incidentally, the first U.S. coin to bear the motto "In God We Trust." The government, evidently feeling frisky in a monetary sort of way, also issued coins in three-cent and twenty-cent denominations during the same period. http://www.word-detective.com/back-k.html#cents

Probably some guy who only had 2 cents to his name

Thats all I have left after selling on ebay and paying all the fees.